Cold wall combustor with flexibly mounted flame tube



Feb. 18, 1958 F. D. BUCKLEY' v 2,823,627

cow WALL COMBUSTOR WITH FLEXIBLY MOUNTED FLAME TUBE Filed Nov. 19, 1951 5 Sheets-Sheet 1 Combos/or;

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flea end Buck/cry I [my Feb. 18, 1958 F. D. BUCKLEY cow WALL COMBUSTOR WITH FLEXIBLY MOUNTED FLAME TUBE 5 shets-sneet 2 Filed Nov. 19, 1951 R .Y mm M w A k m Y w 4 pm Feb. 18, 1958 F. D. BUCKLEY 2,823,627

cow WALL COMBUSTOR WITH FLEXIBLY MOUNTED FLAME TUBE Filed Nov. 19. 1951 5 Shets-Sheet s Q: @Q- Lg w a) Q gm R m N \q\ Q INVENTOR Frederick D.Bucl ly.

BY M J6 4m ATTORNEY Feb. 18, 1958 F. D. BUCKLEY COLD WALL COMBUSTOR WITH FLEXIBLY MOUNTED FLAME TUBE Feb. 18, 1958 F. D.- BUCKLEY cow WALL COMBUSTOR WITH FLEXIBLY MOUNTED FLAME TUBE Filed Nov. 19, 1951 5 Sheets-Sheet 5 2 IN VEN TOR. Frederick D. Buck/ey Mam COLD WALL COMBUSTOR WITH FLEXIBLY MOUNTED FLAME TUBE Frederick D. Buckley, Fredonia, N. Y., assignor to Bituminous Coal Research, Inc., Washington, D. C., a corporation of Delaware Application November 19, 1951, Serial No.- 257,165

4 Claims. (Cl. 110-28) This invention relates to cold wall combustors for the pressurized combustion of fluidized solid fuels as streaming entrainments of pulverulent particles in combustive air streams. More particularly, the invention relates to a novel, air-cooled, flexibly mounted flame tube made from overlapping cylindrical rings, with film-cooling slots therebetween to prevent overheating in the zoneof intense combustion, a radiation shield being spacedly disposed around the flame tube and encased within the combustor casing.

The burning of pulverized coal under gas turbine conditions, to generate motive fluid for the turbines, is a threestage process. First, the coal must be conveyed into the system by a primary stream of compressed air. The aircoal ratio must be kept near one pound of air per pound of coal, and the velocity must be above 50 F. P. S. to prevent the flame from flashing back. Second, the air coal mixture must be introduced into the shielded flame tube by a burner which adds the secondary air necessary to support combustion. Third, after combustion is complete, the remaining excess air is added to bring the air temperature down to a usable level. This three-stage process is further complicated by the fact that the walls of the flame tube must be swept by air to keep the metal below 1500 F., but the cooling air must not be allowed to dilute the flame prematurely. In addition, the burning coal particles must not be allowed to impingeon the walls, in order to prevent accumulations of ash and slag. Finally, the mixing of excess air must be done uniformly to prevent stratification and to freeze all of the ash particles.

The first and third stages of the combustion process, above outlined, are eflfected in a most practical and eflicient manner by the novel flexibly mounted flame tube of the present invention, desirably used in conjunction with the improved annular pulverized coal burner described and claimed in the companion application of Paul M. Rotzler, Ser. No. 257,079 filed November 19, 1951, for Powdered Coal Burner for Pressurized Combustors.

The novel flexibly mounted flame tube of the present invention is embodied in a combustor having a cylindrical casing and a concentric radiation shield spacedly mounted therein, the flame tube being comprised of a series of overlapping stainless steel rings, severally supported by a system of supporting rings. The film-cooled cylindrical bands are flexibly supported by radial pins which pass through the rings. The bands can thus expand freely in a radial direction as they are heated, but they are kept concentric and prevented from moving axially. The ring-supported combustor flame tube of the present invention shows virtually no warping after 250 hours operation, and the film-cooled bands remained concentric.

It is an object of the present invention to provide a cold wall metal combustor having a shielded flame tube which is film cooled and essentially free from warping after extended periods of operation.

It is also an object of the present invention to provide a cold wall combustor having a concentric radiation shield mounting a flame tube comprised of overlapping cylin drical rings with film cooling slots, the rings or film-cooled bands being flexibly supported by radial pins which pass through the rings whereby the bands can expand freely in a radial direction as they are heated, but-are kept concentric and prevented from moving axially.

The above and other desirable objects and advantagesof the present invention will be described in the accompanying specification, a certain preferred embodiment being illustrated in the drawings, by way of example only,

for since the underlying principles may be embodied in other specific structures, it is not intended to be limited to the one here shown, except as such limitations are clearly imposed by the appended claims.

In the drawings, like numerals refer to similar parts throughout the several views, of which Fig. 1 is a schematic showing of a coal-burning,- gas turbine-powered generating electric locomotive power plant incorporating novel combustors of the present invention;

Fig. 2 is an elevation, partly in broken section, of thenovel combustor flame tube herein, and showing the mounting of the burner;

Fig. 3 is an elevation, partly in broken section, of the flame tube of Fig. 2, showing its mounting in a radiation shield;

Fig. 4 is a vertical axial section through a combustor flame tube of the type shown in Fig. 2;

Fig. 5 is a fragmentary showing of a pair of overlapping cylindrical rings and an associated radial supporting pin adjacent the burner end of the combustor flame tube; Fig. 6 is a view similar to Fig. 5, showing the terminal ring and mixing chamber;

Figs. 7 and 8 are cross-sections respectively taken on lines 7-7 and 88 of Fig. 4; a

Fig. 9 is a detail of the mounting of a supporting ring on a longitudinal support, and

10 is a fragmentary detail of the method of connectlng a longitudinal support to a supporting and stiffenmg rib on the mixing chamber.

Turning now to the drawings, and more particularly to Fig. 1, there is shown a coal-burning, gas turbine-powered, generating electric power plant particularly adapted for use in restricted spaces, such as obtain in generating electric locomotives. generally a source of .combustive air-borne fluidized coal 1, a coal splitter 2, a plurality of encased combustors, the casings being designated generally by the numeral 3, and feed lines 4 from the splitter to the combustors. The splitter functions to subdivide the air-borne fluidized coal stream into a plurality of separate streams which are severally delivered to the separate combustors through the individual feed lines 4. The combustors comprise outer casings, usually including radiation shields, as is common in the art, and shown in the above identified Rotzler application, filed of even date herewith, and the novel flame tubes to be described more in detail hereinafter. Motive fluid is delivered from the combustors to ash separator 5 through ducts 6. Cleaned motive fluid is delivered to the turbine 7 through expansion ducts 8 and the expanded gas from the turbine vents to the exhaust stack 9, which mounts a regenerator or heat exchanger 19 in heat-exchanging relation with the stack- A main air compressor 11 is driven by the tur power unit comprising D. C. traction generators 14, and

auxiliary generators 15.

Referring to Figs. 2 and 4,;the suitably encased and flexibly mounted flame tube 20 of the present invention l Patented Feb. 1 8, 1 958 The system, as shown, comprises will be seen to comprise overlapping burner dome rings 21, 22, and, in the form shown, a series of eight overlapping cylindrical rings 23, 23a, 23b, 23c, 23d, 23c, 23 and 23g, of progressively increasing diameter, as shown, and collectively forming the body of the flame tube or combustion chamber proper.

As shown in Figs. 1a, 2, 3 and 4, there is but a slight overlapping of the cylindrical rings by the succeeding rings of progressively increasing diameter. A powdered coal burner, designated generally by the numeral 16, is mounted in the upstream end of the combustor. This burner is more particularly described and claimed in the application of Paul M. Rotzler, hereinabove identified, and will not be described further herein, as no invention, per-se, is predicated on the particular burner structure. The terminal ring 23g of the combustion tube is fitted in and overlapped by the upstream end of the mixing chamber 24, which is provided with an annular series of radial apertures 25 and a closure ring 26 at its downstream end. The ring 26 is hermetically sealed to or otherwise joined with the casing of combustor 3. The relatively short annular spaces formed by and between the successively overlapping cylindrical rings 23 are designated generally by the numeral 27. The upstream edges of the rings are designated generally by the numeral 28, and the downstream edges by the numeral 29. The overlapping rings 23 to 23g, both inclusive, are flexibly mounted for radial expansion and simultaneously held against axial movement, while being maintained concentric, in the following manner:

A plurality of radially disposed, longitudinal stiflening ribs 30, are welded to the outer surface of the mixing chamber 24 of the combustor flame tube. A like number of longitudinal tubular supports 31 are aligned with the ribs 30 and fixedly secured thereto by strap connectors 32, which are welded in the ends of the tubes 31 and attached to the ribs 30 by bolts and nuts, designated generally by the numeral 33. At the burner or dome end of the combustion tube, radial strongbacks or special spacing supporters 34 are severally welded to the upstream end of rings 21, 22, and are secured to the upstream ends of supporting rods or tubes 31, in any suitable manner, as by rivets, or by nuts and bolts, both designated generally by the numeral 35. Thus, it will be seen that the longitudinal supports 31 are firmly held by, and spacedly hold the burner dome ring elements and the mixing chamber, whereby they collectively form a rigidly joined structural entity or cage which is specially adapted to serve as a supporting frame for the flexible mounting of the overlapping film-cooled cylindrical bands or rings comprising the flame tube.

The overlapping, ring-shaped cylindrical flame tube elements are flexibly mounted in the supporting frame of the combustor flame tube in the following manner:

Axially spaced supporting rings or hands 36 are fixedly secured to longitudinal supports 31 by pins or rivets 37, as shown in detail in Fig. 9. These bands are provided with radial apertures 33, midway between the points of attachment of the longitudinal supports 31, and these apertures freely receive sleeves 39 of the flexible mountings 40. The mountings 49 comprise nuts 4-1 welded to the upstream ends of flame rings 2323g, and receiving stud bolts 42 which are screwed therein. As shown in Figs. to 8, the stud bolts and sleeves are of variable length, according to the spacing of the rings they support from the supporting bands 36. The stud bolts 42 extend beyond the bands 36, and lock nuts 43 are threaded over the ends thereof and screwed up to fixedly secure the sleeves 39 against the base nuts 41, which are welded to the flame tube rings. It will be seen that with this arrangement of parts the rings 23-23g are free to move radially, in any direction, as the sleeves 39 slide freely throughthe journaling apertures 38 in the supporting bands 36 of the rigid framework comprised of these bands andlthe longitudinal supports 31.

Turning now to the showing of Fig. 3, the downstream end of the mixing chamber 24 is provided with an integral outer flange 26, conformed to and receiving one end of concentric radiation shield 50. The shield 50 is coexten sive with the flame tube, and its other end extends to the dome section of the flame tube. The shield is provided with longitudinal flutes 51, defining raised, hollow ribs therebetween. The ribs 52 are adapted to slidingly engage the inner surface of the combustor casing, and are adapted to receive the longitudinal stiffening ribs 30 and tubular supports 31 of the cage member in sliding bearing engagement. The flame tube and its radiation shield are suitably mounted in and coaxial with the combustor casing in the usual manner, as well known to those skilled in the art.

It will be seen that with the flame tube made of overlapping cylindrical rings (23--23g) of stainless steel, the

. filmcooling slots 27 will prevent overheating in the Zone of intense combustion.

The slots between the burner dome elements admit the necessary amount of secondary air into the flame tube to complete the combustion. The quenching of the ash and reduction of the temperature of the gaseous products of combustion of the flame are accomplished by admitting the remaining cooling (secondary) air into the flame tube through the large apertures 25 at the downstream end of the mixing section 24 of the flame tube. The inner walls of the flame tube elements are kept substantially free from deposits of ash by the use of the improved annular burner disclosed and claimed in the application of Paul M. Rotzler, hereinabove identified. A particular feature of this burner, when used with a film-cooled, cold wall combustor of the type herein described, is its ability to project a truly axial flame,

' as opposed to a whirling spray type, whereby the ash parments in a substantially rigid cage structure, wherein they are prevented from axial movement, but are permitted radial movement while being maintained concentric, can be said to give rise to a truly floating flame tube ring structure which is self-aligning and self-compensating under all operating conditions. Thus, no matter what type of fuel is burned, and no matter what fuel feed and pressure conditions obtain in the combustor, with' resulting temperature differentials, the novel combustion unit herein will be self-purging and run clean, and with the maximum efficiency.

What is claimed is:

l. A flame tube construction for cold wall combustors, comprising radially arranged longitudinal supporting members, axially disposed supporting bands fixedly secured to and within the longitudinal members, and overlapping flame rings mounted for radial movement in the said bands.

2. In a cold wall combustor having a casing, a radiation shield in the casing, and a concentric combustion unit mounted in the radiation shield and supported thereby and therein, said combustion unit including a burner dome and a terminal mixing chamber, the improvements comprising an intermediate flame tube section in the combustion unit of overlapping cylindrical bands several- 1y secured at their upstream edges to radially movable radial supports mounted in axially fixed supports, the

said axial supports having fixed, radial longitudinal, supports forming a cage.

3. A cold wall combustor comprising a casing; a radiation shield in the casing and defining an annular duct therewith; a combustion chamber mounted in and supported by the said shield, the said combustion chamber having a cylindrical outlet section, a domed inlet section, and a flaring body portion connecting the inlet and outlet sections; the said body portion comprising interfitted, cylindrical annuli, mutually spaced to define annular air passages; supporting means for the said annuli comprising symmetrically disposed radial spacers about the leading edges of the annuli; longitudinal supports secured to the cylindrical outlet section of the combustion chamber and extending to and secured to the domed end thereof; means in said longitudinal supports freely receiving said radial spacers, whereby the annuli are held against axial movement and are radially self-centering; and a burner mounted axially in the said domed end of the combustion chamber.

4. A supporting framework for the interfitted cylindrical flame tube elements of cold wall, cylindrical combustion chambers, comprising a plurality of symmetrical, radially disposed, parallel longitudinal members fixedly secured to the discharge end and to the inlet end of the flame tube, and extending on and over the intermediate cylindrical elements; radial stud members on the said cylindrical elements; and means secured to the longitudinal support members receiving the radial studs in fixed axial spacing, while permitting free radial movement of the said cylindrical elements.

References Cited in the file of this patent UNITED STATES PATENTS 2,268,464 Seippel Dec. 30, 1941 2,448,561 Way Sept. 7, 1948 2,477,583 DeZubay Aug. 2, 1949 2,500,925 Bonvillian et a1 Mar. 21, 1950 2,509,503 Huyton May 30, 1950 2,510,645 McMahan June 6, 1950 2,513,325 Hundstad July 4, 1950 2,547,619 Buckland Apr. 3, 1951 FOREIGN PATENTS 610,641 Great Britain Oct. 19, 1948- 

